ABSTRACT The overall goal of this proposed K99/R00 award is to support my research training so that I can develop into an independent researcher whose work focuses on novel delivery models for effective HIV prevention interventions that operate outside of healthcare clinics. My pre-doctoral, doctoral, and post-doctoral training have given me over a decade of experience in global HIV research and expertise in quantitative methods, randomized trials, HIV self-testing, peer-based interventions, fieldwork, and pre-exposure prophylaxis (PrEP) for HIV prevention. This K99/R00 proposal outlines an intentional training and career development plan that builds on and expands my research skills and experiences so that I can become a competitive applicant for a tenured-track faculty position in an interdisciplinary department, such as global health, at a leading research university. Training plan: To complete my research toolkit and transition to independence, I have assembled a multidisciplinary team of expert mentors from the US and Kenya. Together, we have designed a robust training plan that includes regular mentored meetings and relevant advanced coursework, seminars, workshops, and mentoring groups at the University of Washington and international scientific conferences. The specific training goals for the K99 phase of this award are to: 1) learn how to apply the most commonly used frameworks, strategies, and theories in implementation and behavioral research; 2) develop new and complementary skills in costing methods and qualitative research; 3) conduct formative research and a pilot to develop and refine a peer PrEP referral + HIV self-test (HIVST) delivery model for PrEP initiation among young Kenyan women; and 4) transition to scientific independence by building a publication record in implementation and behavioral science. Research plan: PrEP for HIV prevention is highly effective. However, in Kenya, where the government offers PrEP free of change, few young women at high HIV risk are initiating PrEP. We propose developing, piloting, and testing an innovative model that might overcome barriers to PrEP initiation among young Kenyan women: peer PrEP referral + HIVST delivery. The specific aims of the proposed research are to: 1) develop a peer PrEP referral + HIVST delivery model to facilitate PrEP initiation among young Kenyan women using in-depth interviews with young women informed by implementation frameworks and behavioral theory (Y1); 2) pilot the proposed delivery model and refine the model using focus group discussions with pilot participants informed by implementation frameworks (Y2); 3) test the effect and implementation of the refined delivery model on PrEP initiation and other outcomes (including other metrics of PrEP adoption, model fidelity, and costs) using a hybrid randomized trial (Y3-5). This proposed K99/R00 research directly builds on my previous research experiences, enables me to gain new skills in implementation and behavioral research, addresses one of the greatest challenges to PrEP scale-up today, and will inform an R01 proposal for a community-randomized trial and budget impact analysis.